JPH01303856A - Network controller - Google Patents

Abstract

PURPOSE:To use only one coupling transformer and to reduce the mounting area by providing the coupling transformer taking the impedance matching between a data terminal equipment and a telephone line at the place nearer the data terminal equipment side than that of 1st and 2nd switching circuits in common to the 1st and 2nd transmission circuits. CONSTITUTION:The coupling transformer 101 taking the impedance matching between a data terminal equipment 4 and a telephone line 1 is provided at the place nearer the side of the data terminal equipment 4 than that of the 1st and 2nd switching circuits 7, 12 in common to the 1st and 2nd transmission circuits 1a and 1b. Thus, in case of the communication called from the terminal equipment, the 1st switching circuit 7 closes the 1st data transmission circuit 1a and the coupling transformer 101 takes the impedance matching between the data telephone set 4 and the telephone line 1. furthermore, in case of no ringing communication, the 2nd switching circuit 12 closes the 2nd data transmission circuit 1b and the coupling transformer 101 takes the impedance matching between the data telephone set 4 and the telephone line 1. Thus, one coupling transformer is enough for the controller and the mount area is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a network control device that connects a data terminal device to a telephone line and performs terminal calling communication and no-ringing communication.

<Prior art> In a telemetering system in which data communication is performed between a data terminal device and a center-side device via a telephone line, terminal call origination, which performs communication by making a call from the data terminal device, has recently been developed. In addition to communication, there is no-ringing communication, which reverses the polarity of the subscriber telephone line of the other party's data terminal equipment when a call is made from the center equipment, and communicates without ringing the telephone connected in parallel with the data terminal equipment. It has started to be practiced.

The data terminal device is connected to the subscriber telephone line via the network control device, and the resistance value of the DC circuit formed by connecting the data terminal device to the subscriber telephone line is
It is necessary to set different values in the case of the above-mentioned terminal calling communication and in the case of no-ringing communication due to the difference in the communication method. To give an example, when calling a terminal, the distance is 20m.
The value measured with a current of A or more and 120 mA or less should be 50 Ω or more and 300 Ω or less, and during no-ringing communication, the value should be 4Ω or more when measured with a current of 5+A or more and 20 mA or less.

For this reason, a network control device in a telemetering system that communicates using the two communication methods described above has conventionally had a DC circuit with a resistance value corresponding to each communication method. The connection was switched to the telephone line depending on the situation.

<Problems to be Solved by the Invention> By the way, each of these DC circuits has a switching circuit for controlling the connection with the telephone line, a loop diagnosis circuit for forming a DC resistance, and impedance matching mainly by a coupling transformer. The AC impedance of the impedance matching circuit is the same in both communication methods.
(for example, 600Ω).

Therefore, the above-mentioned conventional network control device has two impedance matching circuits having the same AC impedance, resulting in a problem that the mounting area is large and the cost is high.

Therefore, an object of the present invention is to integrate a coupling transformer, which is a main component of an impedance matching circuit, into one, and to use this coupling transformer for impedance matching for terminal calling communication and no-ringing communication. The purpose of this invention is to provide a network control device that can

Means for Solving the Problems> In order to achieve the above object, the present invention provides a system that, in the case of terminal calling communication in which data communication is performed in response to a calling request from a data terminal device, a calling request from the data terminal device is Thereupon, the data terminal device is connected to a telephone line via a first data transmission circuit including a first switching circuit, the polarity of the telephone line is reversed, and data communication is performed without ringing a telephone set connected to the telephone line. In the case of no-ringing communication,
In response to a call signal sent through a telephone line with reversed polarity, the data terminal device is connected to the data terminal device through a second data transmission circuit that includes a second switching circuit and has a DC resistance different from that of the first data transmission circuit. In a network control device connected to a telephone line, a coupling transformer for impedance matching between the data terminal device and the telephone line is connected to the first. The switching circuit is characterized in that it is provided closer to the data terminal device than the second switching circuit so as to be common to the first transmission circuit and the second transmission circuit.

Effect> In the above configuration, in the case of terminal call communication, the first switching circuit closes the first data transmission path, and the coupling transformer matches the impedance between the data terminal device and the telephone line. Further, in the case of no-ringing communication, the second switching circuit closes the second data transmission path, and the coupling transformer matches the impedance between the data terminal device and the telephone line. Therefore, only one coupling transformer is required for impedance matching between the data terminal equipment and the telephone line, and the mounting area is reduced.

<Example> Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

In FIG. 1, 1 is a telephone line, 2 is a telephone set, 3 is a network control device of this embodiment, and 4 is a data terminal.

The telephone set 2 is connected to the telephone line 1 via a latching relay 5 provided in the network control device 3, and the latching relay 5 is in the "ON" state when data communication is not performed. Telephone 2 is still connected to telephone line 1.

When a calling request is issued from the data terminal 4, the main control circuit 6 of the network control device 3 receives this calling request, turns on the first switching circuit 7, and then turns on the first switching circuit 7. 7. A selection signal for selecting the center side device is sent to the telephone line l via the rectifier circuit 8. Then, when connected to the center side device by this selection signal,
The network control device 3 is connected between the data terminal 4 and the center side device.
Data communication begins via. In the case of this terminal call communication, data from the data terminal device 4 is transmitted to the main control circuit 6, the modulation/demodulation circuit 9, the impedance matching circuit 10,
First switching circuit 7, rectifier circuit 8. is transmitted to telephone line l. Furthermore, data from the center side device is transmitted to the data terminal 4 via the opposite route.

On the other hand, in the case of no-ringing communication in which a call is made from the center side device, the polarity of the telephone line l is first reversed, and the voltage level of the circuit 1a becomes higher than the voltage level of the circuit 1b, which is then passed through the diode 11 to the second switching circuit. 12 is activated. Next, when a call signal is sent from the center side device, the call signal detection circuit 13 detects the call signal and notifies the main control circuit 6 of the detection. The main control circuit 6 activates the third switching circuit 14 in response to the notification from the calling signal detection circuit 13, and then sends a response signal from the response signal sending circuit 15 to the center side device while calling the data terminal 4. let

After the center side device receives the response signal, data communication is performed between the center side device and the data terminal 4 via the network control device 3. In the case of this no-ringing communication, data from the data terminal 4 is transferred to the main control circuit 6.
, a modulation/demodulation circuit 9, an impedance matching circuit 10. , A.C.
Cub-pulling capacitor 16, third switching circuit 1
4. The signal is sent to the telephone line l through the second switching circuit f2 and the diode II. Furthermore, data from the center side device is transmitted to the data terminal 4 via the opposite route.

The values of DC resistance and AC impedance of the DC circuit during communication required in the case of the terminal calling communication and no-ringing communication are the values of the first switching circuit 7, the impedance matching circuit 10, the third switching circuit 14, and the AC coupling circuit. A loop circuit control section 19 consisting of a capacitor 16 and a half-loop circuit 17 satisfies this requirement.

Details of the loop circuit control section 19 are shown in FIG. 2. As shown in FIG. 2, the first switching circuit 7 is a switching transistor? ! ,resistance? 2, 73, 74 and a photocoupler 75. In the case of terminal call communication, the switching transistor 71 becomes conductive, and the sum of the DC resistance on the first switching circuit side of the coupling transformer 101 forming the impedance matching circuit 10 and the limiting resistance 72 of the first switching circuit 7 is turned on. This satisfies the resistance value required for terminal call communication, and AC impedance matching is achieved by the coupling transformer 101.

Further, the third switching circuit 14 includes switching transistors 141 . Resistor 142.143 and photocoupler 1
It has been established since 44. In the case of no-ringing communication, the switching transistor 141 becomes conductive, the half-loop circuit 17 satisfies the resistance value required for no-ringing communication, and the AC coupling capacitor 16, coupling transformer 101, and half-loop circuit 17 perform AC impedance matching. I try to take it.

In this way, since the coupling transformer lO1 for impedance matching is used in both terminal call communication and no-ringing communication, the coupling transformer is not needed, and the mounting area is small and the cost is low. becomes.

In the above embodiment, the DC resistance value required for terminal call communication is satisfied by the limiting resistance 72 of the first switching circuit 7 and the resistance on the first switching circuit 7 side of the coupling transformer 101. As shown in FIG. 3, a coupling transformer 101 may be connected with a capacitor 102 and a loop forming circuit 103 may be provided so that the loop forming circuit 103 and the limiting resistor 72 satisfy the above DC resistance value.

<Effects of the Invention> As is clear from the above, the network control device of the present invention uses a coupling transformer for impedance matching between a data terminal device and a telephone line to connect the data terminal to the data terminal in the case of terminal call communication. The first data transmission path is common to a first data transmission path connecting the device to a telephone line and a second data transmission path connecting the data terminal device to the telephone line in the case of no-ringing communication, and The first included in the road
Since it is provided closer to the data terminal device than the switching circuit and the second switching circuit included in the second data transmission path, only one coupling transformer is required, resulting in a small mounting area and low cost.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the circuit configuration of one embodiment of the present invention, FIG. 2 is a detailed circuit diagram of the loop circuit control section in the above embodiment, and FIG. 3 is another impedance matching circuit in the above embodiment. It is a figure which shows an example. l... Subscriber telephone line, 2... Telephone, 3... Network control device, 4... Data terminal, 7... First switching circuit, ! 0... Impedance matching circuit, 12... Second switching circuit, 14... Third switching circuit, 17... Half loop circuit, 71.141... Switching transistor, 72...
...Limiting resistance, lot...coupling transformer.

Claims (1)

[Claims] (1) In the case of a terminal calling communication in which data communication is performed in response to a calling request from a data terminal device, the data terminal device receives a calling request from the data terminal device and transmits data to the data terminal device including a first switching circuit. In the case of no-ringing communication, in which the telephone line is connected to a telephone line through a circuit, the polarity of the telephone line is reversed, and data communication is performed without causing the telephone connected to the telephone line to ring. A network control device configured to connect the data terminal device to a telephone line via a second data transmission circuit that includes a second switching circuit and has a DC resistance different from that of the first data transmission circuit in response to an incoming call signal. A coupling transformer for impedance matching between the data terminal device and the telephone line is connected to the first and second
A network control device characterized in that it is provided closer to a data terminal device than a switching circuit so as to be common to the first transmission circuit and the second transmission circuit.